Competitive Mega Steelix?

[Geowlett]

Im wanting to make a competitive steelix, but i want to know a good setup that doesnt have a jolly nature. Im not good at things like this so i need help. It will have 5 perfect IVs (maybe 6 if im lucky). But i need a nature, ability, and moveset.

 

[Alfieri]

When in doubt I use Smogon to get me started and go from there. This is their current set for SM:

Steelix @ Steelixite
Ability: Sturdy
EVs: 252 HP / 4 Def / 252 SpD
Careful Nature
- Stealth Rock
- Heavy Slam
- Earthquake
- Toxic

Makes sense not to invest in defense EVs since its natural defense is overkill. Max HP so it can take those physical hits with ease. Stealth rock for standard hazards, toxic for stalling, heavy slam because he's heavy AF and Earthquake for good STAB.

Feel free to change things around for whatever fits your team's needs better. But focusing on his special defense and being a staller while hitting well is a perfect role for it.